Typically, utilizing a master gaming controller, a gaming machine controls various combinations of devices that allow a player to play a wager game on the gaming machine and also encourage game play on the gaming machine. For example, a wager game played on a gaming machine usually requires a player to input money or indicia of credit into the gaming machine, indicate a wager amount, and initiate a game play. These steps require the gaming machine to control payment devices, including bill validators and coin acceptors, to accept money into the gaming machine and recognize user inputs from user interfaces, including key pads, button pads or touch screens, to determine the wager amount and initiate game play. After game play has been initiated, the gaming machine determines a wager game outcome, presents the game outcome to the player and may dispense an award of some type depending on the outcome of the wager game.
Modern gaming machines make liberal use of lights to enhance the visual experience of the player as well as to convey information regarding game events to the player. Groups of lights in a common location within the game machine are often connected to a common circuit board, or lighting board, which controls the operation of the lights. The lighting board selectively operates each light based on instructions received from the master gaming controller over a communications, or light bus. The light bus connecting the master gaming controller to the lighting board carries a clock signal to synchronize data sent along the bus. The light bus may be several feet long and a major source of EM emissions from the game machine.
The EM emissions from the light bus have a pronounced energy peak at a fundamental frequency equal to the frequency of the clock signal, and also at harmonics of the fundamental frequency. Radiation at these frequencies can interfere with other carrier signals and devices. Such interference is known as electromagnetic interference (EMI).
The Federal Communication Commission (FCC) rules limit EM emission levels for gaming machines over a range of frequencies. In gaming machines, when emission is excessive at one or more frequencies, remedies that may be effective in lowering emissions include adding shielding components, adding ferrite clamps to harnesses (both inter-assembly signal harnesses and power/ground harnesses), improving grounding connections between system components, and board redesigning to add key signal filtering, improve on-board power/ground handing, or incorporate various signal integrity improvement techniques at the board level. These solutions often increase system cost because of added material, manufacturing, and labor costs. Furthermore, sometimes these remedies are not reliably replaced after system field maintenance because leaving them out has no detrimental effect on the functional operation of the gaming machine.
For the foregoing and other reasons, it would be desirable to provide novel methods and devices for reducing EM emission levels at low cost in gaming machines that are not subject to inadvertent removal or disablement.